I am trying to learn about photography, and I read something saying the RAW (for example, DNG) file format has detailed information about the image. I wonder if anyone can tell me: how do I know a camera is able to take RAW images?
It's true that raw files contain much more information than jpeg files and that this information is very useful when editing the photo.
DNG (digital negative), is just one raw format, it was developed by Adobe and is intended to be a generic format that everyone is supposed to use - however, camera manufacturers don't share Adobe's worldview and almost none of the major camera manufacturers support DNG.
Canon has CR2, Nikon has NEF, etc.
What you are looking for is "raw support" (not DNG support) and all cameras except for the most basic point and shoots have it.
For a starting point, check out What is RAW, technically? —
DNG, the "digital negative" format you mention, is Adobe's attempt at making a standard, but actually almost all camera makers have their own RAW formats, with different extensions like
.NEF, and so on (see a list at Wikipedia). There's really nothing special that
DNG does that the maker-specific RAW formats can't also do, and most third-party software supports almost all formats. (See Is switching to DNG worthwhile? for more on that.)
So, in general, you want to look for "raw support". This is commonly recognized as an important feature, and all camera specs, reviews, and databases will tell you. For example, you can look at Neocamera's search for cameras with RAW support, and narrow down from there. (You can also search for specifically
.DNG support of that's important to you.
Also, for basic background on why you might want to use RAW, check out Good examples of RAW's advantages over JPEG? (which happens to be the top-voted question and has the top-voted answer on this site), and the raw-vs-jpeg tag for even more.
This page on Adobe's website lists all cameras with built-in DNG support, as well as all cameras with a proprietary RAW format supported by Adobe tools:
It simply says so in the specifications.
Each site presents it differently though. For example on Nikon's own specifications for the D7100, it says next to Image Formats:
NEF (RAW): 12 or 14 bit, lossless compressed or compressed
On Neocamera, I present this in simplified form for all cameras exactly the same way. Here it is for the Nikon D7100 for example and, next Image Formats, it says:
If you were to look at a camera not supporting RAW, it would simply say
Now, unless you have a model in mind, you will find it tedious to check each page. So instead, you can simply search for cameras which support RAW (or DNG specifically) using the Camera Search page. Just select your criteria an check the RAW or DNG box.
Note also, that RAW describes a general format, it's not the implementation. That's why you have so many different types of RAW. Every camera will tell you on the box,--or you can look it up on B&H's website for any camera they sell under "Product highlights."
If you use Lightroom and probably, you can convert to DNG, if you need it for some reason (can't imagine why at present other than for moving files around or archive purposes),--you don't need to have it in the camera. Wouldn't convert everything to DNG just yet though: some viewers still don't seem to open them.